Normal Processing Temperatures Research Articles

Application of Tamarind Shell as a Green Additive in Natural Rubber.

The feasibility of using tamarind shell as an eco-friendly additive in natural rubber (NR) was studied. Tamarind shell powder (TSP) was prepared with different particle size ranges before being characterized by various techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis, etc. The results of the FTIR and elemental analysis confirmed that TSP was mainly composed of amino acids (proteins), celluloses, and tannins. The thermal analysis revealed that TSP contained approximately 9% moisture, and its main constituents were stable up to 200 °C, which is higher than the normal processing temperature of rubber products. The addition of TSP to NR led to reductions in scorch time and cure time due to the presence of moisture and proteins. This phenomenon was more obvious with the decrease in TSP's particle size. Even though the small addition of TSP (≤10 phr) did not cause any change in hardness, it significantly impaired the mechanical properties of the rubber vulcanizates, particularly tensile strength, elongation at break, and abrasion resistance. Such deterioration depended greatly on the TSP particle size, i.e., the finest particles (S-TSP) showed the least deterioration of mechanical properties. In summary, TSP can be considered a low-cost, eco-friendly bio-additive for rubbers. Nevertheless, it must be used with great care to avoid undesirable impacts on mechanical properties.

Improving flushing processes through targeted control of the temperature boundary conditions

AbstractIn this contribution the authors investigate how flushing of chocolate using a follow‐up chocolate in a straight horizontal pipe is affected by temperature. The authors investigate a non‐uniform distribution of temperature across the considered domain. This is done using two cases, where the first exhibits a wall temperature deviating from the normal process temperature and the second exhibits a differently tempered follow‐up chocolate. The investigations are performed using unsteady three‐dimensional numerical simulations with an OpenFOAM multiphase solver, which is extended to include an additional equation for energy conservation. The physical properties of the chocolate are analyzed with respect to their dependence on temperature and implemented in a new model in OpenFOAM. The results of both cases are assessed according to industrially relevant questions. Among others, they include the amount of follow‐up chocolate needed to achieve a set goal of cleanliness. The time needed to achieve this is also considered. A dimensionless time is used to compare the different cases. Recommendations are provided on how different temperature of pipe wall and follow‐up chocolate may lead to improved flushing processes and which savings may be achieved with this strategy.

Investigation of thermal and mechanical properties of new nitrogen-rich organic based heat stabilizers for poly (vinyl chloride)

Urea cyanurate, as a new nitrogen-rich organic-based heat stabilizer, for the enhancement to thermal properties of polyvinyl chloride (PVC) is prepared via the simple precipitation method, in this study. Characterization, thermal and mechanical properties of the stabilized PVC were examined by means of fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTG), X-ray photoelectron spectroscopy (XPS) measurements, discoloration test, congo red test and the weight-loss method, thermal aging test, and tensile analysis. Results showed that the thermal stability of PVC is improved after the addition of urea cyanurate in PVC formulation and weight loss related to HCl releasing in the normal PVC processing temperature (180°C) is less than 1%. Enhancement of the thermal properties and stability time of the PVC lead to decreased degradation tendency. Oven-aging test result showed that the color change during degradation process of PVC samples improved by adding the urea cyanurate. The tensile strength of stabilized samples were about 42%, higher as compared to the pure PVC. The optimum and best results for improving the thermal and mechanical properties of PVC were obtained by incorporating the 3 wt % of the urea cyanurate.

Synergies between phosphomolybdate and aluminum diethylphosphinate acting as temperature-response microparticles for promoting fire safety of epoxy resin

In this work, ammonium phosphomolybdate (AMP) and aluminum diethylphosphinate (ADP) acting as temperature-response microparticles, were incorporated into epoxy resin (EP) together to promote fire safety and dynamic mechanical performance of EP composites at the same time. Both ADP and AMP acted as chemical inertness fillers to enhance the EP matrix at the normal service temperature and processing temperature. When the temperature rose after heating or even burning, both ADP and AMP presented chemical functions. On one hand, AMP exhibited excellent catalytic charring activity and smoke suppression efficiency. On the other hand, the combination between AMP and ADP in the EP/AMP/ADP composites showed excellent synergistic effects in improving the flame retardancy of EP. Compared to the case of EP, the peak heat release rate (PHRR) of EP/AMP/ADP composites (1.2 wt% AMP and 3.6 wt% ADP) was decreased by 54%, the total heat release (THR) was reduced by 25%, and the total smoke production (TSP) was reduced by 25%. Meanwhile, the UL-94 V-0 rating was obtained, and the limiting oxygen index (LOI) of the composite was increased from 26.2 to 31.2%. The mechanism of flame retardancy was analyzed and discussed. In addition, compared with EP, EP/AMP/ADP composites showed a higher dynamic mechanical property without affecting the glass transition temperature.

Small-scale bioreactor supports high density HEK293 cell perfusion culture for the production of recombinant Erythropoietin

Process intensification in mammalian cell culture-based recombinant protein production has been achieved by high cell density perfusion exceeding 108 cells/mL in the recent years. As the majority of therapeutic proteins are produced in Chinese Hamster Ovary (CHO) cells, intensified perfusion processes have been mainly developed for this type of host cell line. However, the use of CHO cells can result in non-human posttranslational modifications of the protein of interest, which may be disadvantageous compared with human cell lines.In this study, we developed a high cell density perfusion process of Human Embryonic Kidney (HEK293) cells producing recombinant human Erythropoietin (rhEPO). Firstly, a small-scale perfusion system from commercial bench-top screening bioreactors was developed for <250 mL working volume. Then, after the first trial runs with CHO cells, the system was modified for HEK293 cells (more sensitive than CHO cells) to achieve a higher oxygen transfer under mild aeration and agitation conditions. Steady states for medium (20 × 106 cells/mL) and high cell densities (80 × 106 cells/mL), normal process temperature (37 °C) and mild hypothermia (33 °C) as well as different cell specific perfusion rates (CSPR) from 10 to 60 pL/cell/day were applied to study the performance of the culture. The volumetric productivity was maximized for the high cell density steady state but decreased when an extremely low CSPR of 10 pL/cell/day was applied. The shift from high to low CSPR strongly reduced the nutrient uptake rates. The results from our study show that human cell lines, such as HEK293 can be used for intensified perfusion processes.

A study of the thermal degradation of glass fibre sizings at composite processing temperatures

Although not fully understood, it is well recognized that optimal working of glass fibre sizings is necessary to maximize the performance of glass fibre reinforced polymer composites. It is important that the organic components in such sizings continue to function after exposure to the high temperatures often experienced during composite processing. This study presents the results on the thermal stability of polypropylene and epoxy compatible glass fibre sizings obtained using TGA, microbond adhesion measurement and composite mechanical testing. Test results indicate that the performance of commercial polypropylene compatible glass fibre sizings can be significantly compromised by thermo-oxidative degradation at normal composite processing temperatures. A significant reduction in composite performance is directly related to a loss of fibre-matrix adhesion caused by thermal degradation of some of the principal sizing components.

Thermal, thermo-oxidative and thermomechanical degradation of PLA: A comparative study based on rheological, chemical and thermal properties

This research studies the effect of thermal, thermo-oxidative and thermomechanical degradation conditions on the melt rheological, chemical and thermal properties of PLA at temperatures around its normal processing temperature. Thermal and thermo-oxidative degradations were conducted on a rheometer by using nitrogen or air as gas, respectively, and the thermomechanical degradation was performed on a mixer equipped with two counter-rotating rollers. Dynamic oscillatory rheology, TGA, DSC and FTIR were performed on PLA samples subjected to different degradation conditions: temperature (180, 200 or 220 °C), time (15, 30 or 60 min), atmosphere (air or atmosphere) and the application of mechanical stress or not. Thus, rheological results indicate the synergic effect that temperature, mechanical stress and time exerts on the extent of chain scission phenomena, which was also corroborated by FTIR results; however, the individual contribution of mechanical stress diminishes gradually with the degradation time, being more pronounced for higher degradation temperature. In addition, degree of crystallinity (χc) turned out not to be a suitable parameter for comparing degraded samples, since all of them became amorphous after degradation. Instead, glass transition (Tg) and cold crystallization (Tcc) temperatures as well as the cold crystallization enthalpy (ΔHcc) reveal that the chain scission phenomena makes degraded samples easier to crystallize. Finally, TGA results point out a worsening of the PLA thermal stability, with lower values of the characteristic temperatures (T5% and Tmax) for degraded samples.

New extraction process for recovery of metals in glass deposits

A new process, named salt extraction process, has been developed to enable recovery of metal values from secondary sources e.g. scrap and waste materials such as slag and flue dust. It is also feasible in extracting metals from certain ores that normally are difficult to enrich and process by traditional metallurgy – two examples are nickel and cobalt. The salt extraction process has also been applied in the recovery of metals from silicates including lead from glass wastes.The process is based on the extraction of metal values from the raw materials into a molten salt bath consisting of NaCl, LiCl, and KCl corresponding to the ternary eutectic composition and with AlCl3 dissolved in the salt melt acting as the chlorinating agent. This is followed by the electrolysis of the salt bath in the same reactor. The normal processing temperature is in the range 973 K (700 °C) to 1173 K (900 °C). The aluminium chloride in the salt bath reacts with the metals in the fine comminuted raw material and metal ions are formed in the chloride bath. During the electrolysis, the metal ions reach the solid cathode and get deposited in metallic form. Liquid aluminium is used as the anode. Chlorine gas formed at the anode reacts with aluminium forming aluminium chloride in situ, which gets dissolved in the salt melt supplying the required amount of the flux.The salt extraction process has been used successfully in the extraction of Cr and Fe from electric arc furnace (EAF) silicate slag. Experiments have also been carried out in which lead has been recovered with high yield from spent cathode ray tubes. The process was shown to be successful in the extraction of the rare-earth metals neodymium and dysprosium from permanent magnet scrap. The method is a highly promising process route for the recovery of strategic metals. It also has the added important advantage of being environment-friendly, with only small amount recyclable, potentially useful rest products like alumina and silica as with limited energy consumption.

Warm Incremental Forming of Magnesium Alloys Using Hot Fluid as Heating Media

Industrial application of magnesium alloys is increasing in the last decade due to the very high mechanical strength to weight ratio they present. Typical applications are aeronautic parts but their use in the automotive industry is also growing. The bigger the reduction of the vehicle weight is, which can be obtain using these alloys, the bigger the energy saving will be in the near future. However, the formability of these alloys is poor and they are very difficult to be formed at room temperature. Several works have been presented by different authors on the positive influence the temperature increase has to form magnesium alloys. Normal process temperature is about 200-250°C. In this paper warm incremental forming of magnesium alloys is investigated. The work focuses in the formability limits of the alloys and the identification of the optimal process parameters. Aiming to obtain a homogeneous temperature in the forming areas, hot fluid is used as heating media. Experimental results for different temperatures are presented and final microstructures are related to the possible deformation mechanism.

Factors Influencing Diameter of Polypropylene Fiber in Melt Electrospinning

Melt electrospinning is a safer, more environmentally friendly and cheaper alternative to solution electrospinning in producing superfine fibers. In this paper, a novel melt electrospinning device was used, which has higher efficiency than conventional equipment. Polypropylene is widely used in many fields and it is difficult to find a suitable solvent for its solution electrospinning at room temperature, so it was chosen in this study. The influences of the electrospinning parameters such as temperature and voltage on the diameter of the spinning fibers have been studied. Temperatures higher than normal processing temperatures were used in present electrospinning system in order to reduce the viscosity of the polymer melt sufficiently. Good quality fibers with smooth surfaces and with diameters mostly smaller than 10 microns were spun successfully. It was found that there was an optimum point for the spinning voltage (70-80KV) and the temperature (230-260°C) to get fine fibers.

Melt electrospinning of low‐density polyethylene having a low‐melt flow index

AbstractMelt electrospinning is a cheaper, more environmentally friendly, and safer alternative to solution electrospinning. We have designed a novel melt spinning device which incorporates a reverse of the normal polarity, with the capillary grounded and the collector grid at positive potential. The apparatus is much simpler and more economical than conventional equipment because no syringe pump is required. Low‐density polyethylene (LDPE) with a low‐melt flow index of 2 g/10 min, which is not suitable for spinning using current commercial methods, was chosen to highlight the advantages of melt electrospinning in general, and our device in particular. The effects of varying the electrospinning parameters such as temperature, electrostatic field, spinning distance, and capillary inner diameter, have been studied. Although it was found that temperatures higher than normal processing temperatures had to be employed in our electrospinning system to reduce the viscosity of the polymer melt sufficiently, good quality fibers with smooth and even surfaces, most of which had diameters smaller than 15 μm, were electrospun successfully. It was observed that there was an optimum point for the spinning distance (14–15 cm) and the capillary inner diameter (0.4–0.6 mm) to get fine fiber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Influence of moisture on BCN (low- K) film for interconnection reliability

The integration of low dielectric constant (low- K) interlayers and Cu wiring is necessary to produce next-generation LSI devices. Low- K films of porous type have been investigated to reduce a dielectric constant ( K value). However, most porous low- K materials have faced a serious problem of water incorporation during the wet processes used in making the interconnections. Thus, the influence of moisture on boron carbon nitride (BCN) films is important to investigate. To study water-treated BCN films, we measured the current-versus-voltage (I–V) and capacitance-versus-voltage (C–V) characteristics of BCN films, using an MIS (mercury electrode/BCN/Si substrate) structure. We found that both the leakage current and dielectric constant of BCN films decrease as the film's carbon-composition ratio increases. D 2O detection using thermal desorption spectroscopy (TDS) reveals that BCN films with carbon-composition ratios greater than 30% can suppress the incorporation of water into the film. Desorption of hygroscopic water from the BCN film occurred at temperatures as low as 390 °C, which is a normal LSI-production process temperature. The use of BCN film appears to resolve the serious problem of water incorporation into the porous low- K materials. In addition, we have investigated a conduction mechanism resulting from the water protons, based on the frequency dependence of the BCN film impedance before and after water treatment.

Combined AES and TOF‐SIMS analysis of a thermally treated Ag/Ti/Al metallization system

AbstractBoth Auger electron spectroscopy (AES) and time‐of‐flight secondary ion mass spectroscopy (TOF‐SIMS) were applied to study a three‐layer backside metallization stack that was thermally treated up to temperatures above the normal process temperature. In addition to conventional sputter depth profiling, we applied a more sophisticated sample preparation method—in situ low angle cross sectioning. This way the depth scale was enlarged approximately by a factor of 20, and therefore transferred to lateral dimensions. This allows a more detailed AES analysis of the metallization system using mappings of elemental distributions. The TOF‐SIMS depth profiles were recorded as a function of the lateral geometric coordinates and in depth as a function of the sputter ion dose. This way it was possible to analyse the three‐dimensional sample composition. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Catalytic decomposition of hydrogen peroxide in the presence of alkylpyridines: Runaway scenarios studies

A number of runaway scenarios of the excess of hydrogen peroxide used during the N-oxidation of alkylpyridines, under closed and open conditions, were examined. It was found that, in most cases, if the volume of the liquid hydrogen peroxide solution occupies more than 10% of the total volume of a closed system (e.g. reactor and vent line between reactor and blockage), the production of gases raises the pressure so quickly that evaporation is completely suppressed. Higher than 70% filling levels result in complete expansion of the liquid. The MTSR(t) of the system falls rapidly if the normal process temperature is high, but if a runaway occurs exactly at the end of dosing, MTST will be very high and secondary decompositions will rapidly develop. The results of this study are currently being used to critically assess the current approaches and further the study of inherently safer designs.

Thermal stability of dopants in laser annealed silicon

As semiconductor device dimensions continue to decrease, the main challenge in the area of junction formation involves decreasing the junction depth while simultaneously decreasing the sheet resistance. Laser annealing is being investigated as an alternative to rapid thermal annealing to repair the damage from ion implantation and to activate the dopants. With this technique, uniform, box-shaped profiles are obtained, with dopant concentrations that can exceed equilibrium solubility limits at normal processing temperatures. Unfortunately, these super-saturated dopant concentrations exist in a metastable state and deactivate upon further thermal processing. In this article, we describe a comprehensive study of the deactivation kinetics of common dopants (P, B, and Sb) across a range of concentrations and annealing conditions. For comparison, As deactivation data from the literature is also presented. P and As deactivate substantially at temperatures as low as 500 °C, while Sb at moderate concentrations and B remain fully active until 700 to 800 °C. It is proposed that As and P deactivate through the formation of small dopant-defect clusters while B deactivates through precipitation. The proximity to the surface is shown to be a second-order effect.

TlSr2CaCu2Oy template for the growth of superconducting Tl(Ba, Sr)2Ca2Cu3Oy thin films on CeO2 buffered sapphire

Thin films of Tl(Ba, Sr)2Ca2Cu3Oy superconductor have been grown on CeO2 buffered r-cut sapphire substrate with the use of a template TlSr2CaCu2Oy by the amorphous phase epitaxy method. By using this template containing Sr, we have overcome the problem of chemical reactions between Ba and Ce present in the superconducting and buffer layers, respectively, at the normal processing temperatures of 840–890 °C. Films grown by this method have an excellent c-axis orientation as well as in-plane alignment with the TlSr2CaCu2Oy template, which in turn is aligned with the CeO2 layers. These films have superconducting critical temperature values up to 104 K and critical current density values as high as 1 MA cm−2 at 77.3 K and 0 T.

Evolution and Kinetics of Volatile Organic Compounds Generated during Low-Temperature Polymer Degradation

A method using direct flame ionization detector (FID) measurement was developed to study total volatile organic compound (VOC) emissions during thermal degradation of polymers. This method was used to estimate organic emissions from different polymers, such as low-density polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and commingled postconsumer streams, such as recycled carpet residue and auto shredder residue (ASR). The effects of process parameters, such as temperature, heating rate, and residence time, were also studied. Significant VOC emissions were observed at normal processing temperatures, particularly from recycled polymers. Each polymer showed a distinct evolution pattern during its thermal degradation. The kinetics of VOC emissions were also studied using a nonisothermal technique. The kinetic parameters were in agreement with data from the literature.

Prediction of the consolidation of woven fibre-reinforced thermoplastic composites. Part I. Isothermal case

The mechanisms involved in the isothermal consolidation of woven carbon fibre-reinforced polyetherimide (PEI/WCF) have been studied. Press-formed samples were processed in a matched-die mould equipped with pressure and temperature transducers. Optical microscopy and fracture tests were used to determine the evolution of consolidation as a function of three processing parameters namely pressure, temperature and time. The mechanisms of intimate contact and fibre impregnation were found to be responsible for void resorption. At normal processing temperatures the inter-ply interfacial strength is governed by resin flow at the interface and the mechanism of fibre impregnation limits the rate of consolidation. A model which accounts for resin flow through the fibre bed, for the formation of intimate contact and for autohesion between adjacent plies has been proposed to predict the consolidation of PEI/WCF. Predictions obtained using this model have shown good agreement with experimental results.

Thermal stability of PEEK/carbon fiber in air and its influence on consolidation

AbstractThe thermal stability of carbon fiber‐reinforced polyetheretherketone (PEEK/CF) in air and its influence on consolidation are characterized under simulated processing conditions. The changes in dynamic shear modulus, melting temperature, heat of fusion and glass transition temperature due to chemical reactions and morphology changes were monitored by dynamic rheological analysis and differential scanning calorimetry. Thermal decomposition in air and simultaneous thermooxidative reaction of PEEK resin exposed to temperatures slightly higher than normal processing temperatures were observed by thermogravimetric and dynamic rheological analysis. The initial stage of this thermo‐oxidative reaction, under isothermal and non‐isothermal conditions, was modeled by a exponential‐based Arrhenius expression. The consolidation of PEEK/CF is affected by the thermal oxidation of the resin, which delays time to intimate contact between the plies. A consolidation model, predicting the degree of intimate contact, is extended to also take into account the rheological changes of the system. Finally, a processing limit regarding the thermal stability is defined based on the model and the experimental results.

Influence of the [formula omitted] molar ratio on the structural and electronic properties of MOVPE grown GaN

Low pressure MOVPE has been used to grow a series of GaN epilayers, deposited onto (0001) sapphire substrates. All the growth parameters have been kept constant, except for the V III molar ratio, which has been changed from sample to sample by changing the ammonia flow rate. The growth rate has been measured vs the V III molar ratio at both low temperature (550°C, growth of the buffer layer) and normal process temperature. A strong dependence of the growth rate vs the V III molar ratio is found at both temperatures. Systematic photoluminescence and reflectivity experiments have been performed at 2 K on all samples. The photoluminescence is dominated by the donor bound exciton and donor acceptor pair are visible on samples grown under the lowest V III molar ratio, indicating higher impurity incorporation. An optimum V III molar ratio of 5000 is proposed, which corresponds to the highest growth rate observed and to the lowest full width at half maximum for the photoluminescence line.